Top surface imaging technique for top pole tip width control in magnetoresistive read/write head processing

ABSTRACT

A top surface imaging technique for top pole tip width control in a magnetoresistive (“MR”) or giant magnetoresistive (“GMR”) read/write head is disclosed in which a multi-layer structure is employed to define the thick photoresist during processing resulting in much improved dimensional control. To this end, a relatively thin upper photoresist layer is patterned with much improved resolution, an intermediate metal or ceramic layer is then defined utilizing the upper photoresist layer as a reactive ion etching (“RIE”) mask, with the intermediate layer then being used as an etching mask to define the bottom-most thick photoresist layer in a second RIE process. As a consequence, a much improved sub-micron pole tip width along with a high aspect ratio and vertical profile is provided together with much improved critical dimension control.

CROSS REFERENCE TO RELATED PATENTS

The present application is a divisional application of co-pending U.S.patent application Ser. No. 09/177,901, filed Oct. 23, 1998 entitled TOPSURFACE IMAGING TECHNIQUE FOR TOP POLE TIP WIDTH CONTROL INMAGNETORESISTIVE READ/WRITE HEAD PROCESSING, now U.S. Pat. No.6,156,487.

The subject matter of the present invention is related to that disclosedin U.S. Pat. No. 5,485,334 for “Magnetoresistive Device and MethodHaving Improved Barkhausen Noise Suppression”; U.S. Pat. No. 5,532,892for “Soft Adjacent Layer Biased Magnetoresistive Device Incorporating aNatural Flux Closure Design Utilizing Coplanar Permanent Magnet ThinFilm Stabilization”; U.S. Pat. No. 5,573,809 for “Process for Forming aMagnetoresistive Device”; U.S. Pat. No. 5,608,593 for “Shaped Spin ValveType Magnetoresistive Transducer and Method for Fabricating the SameIncorporating Domain Stabilization Technique”; U.S. Pat. No. 5,634,260for “Method of Making a Magnetoresistive Device Having ImprovedBarkhausen Noise Suppression”; U.S. Pat. No. 5,637,235 for “Shaped SpinValve Type Magnetoresistive Transducer and Method for Fabricating theSame Incorporating Domain Stabilization Technique”; U.S. Pat. No.5,639,509 for “Process for Forming a Flux Enhanced Magnetic DataTransducer”; U.S. Pat. No. 5,654,854 for “Longitudinally BiasedMagnetoresistive Sensor Having a Concave Shaped Active Region to ReduceBarkhausen Noise by Achieving a Substantially Single Magnetic DomainState”; U.S. Pat. No. 5,658,469 for “Method for Forming Re-EntrantPhotoresist Lift-Off Profile for Thin Film Device Processing and aThin-Film Device Made Thereby”; and U.S. Pat. No. 5,668,688 for “CurrentPerpendicular-to-the-Plane Spin Valve Type Magnetoresistive Transducer”,the disclosures of which are herein specifically incorporated by thisreference.

BACKGROUND OF THE INVENTION

The present invention relates, in general, to the field ofmagnetoresistive (“MR”) and giant magnetoresistive (“GMR”) read/writeheads. More particularly, the present invention relates to a techniquefor top surface imaging for top pole tip width control in MR write headprocessing.

Top pole tip definition for the write transducer portion of a read/writehead and its critical dimension (“CD”) control currently present majorchallenges in thin film MR/GMR head processing. As the demand for evermore storage capacity in disk drives intensifies resulting in the needfor real recording densities of on the order of 20,000 to 35,000 tracksper inch (“TPI”) and greater, future generations of these heads mustthen exhibit a track width which is increasingly reduced whilenevertheless maintaining a high stack height for performance reasons.

As a consequence, these constraints imply that the critical dimensionsof the top pole tip of the write head must be in the sub-micron range ofon the order of 0.30 to 0.8 microns (“μm”). However, utilizing currentthin film photolithography techniques and steppers, it is extremelydifficult to pattern tip widths of such narrow dimensions while alsoproviding high aspect ratios and vertical profiles together with tightcritical dimension control due to the limitation of resolution inherentin a conventional thick photoresist pattern of on the order of 6.0μm-10.0 μm. While conventional processing can be used in conjunctionwith a slider level pole trim operation as one way to achieve asub-micron write track width, such an operation is extremely costly in amanufacturing environment with the further possibility that it caneasily result in damage to the associated MR and/or GMR read sensor.

SUMMARY OF THE INVENTION

In accordance with the technique of the present invention a top surfaceimaging technique for top pole tip width control is disclosed in which amulti-layer structure is employed to define the thick photoresist withmuch improved dimensional control. To this end, a relatively thin upperphotoresist layer is patterned with much improved resolution, anintermediate layer of ceramic or metal is then defined utilizing theupper photoresist layer as a reactive ion etching (“RIE”) mask, with theintermediate layer then being used as an etching mask to define thebottom-most thick photoresist layer by a second RIE process. As aconsequence, a much improved sub-micron pole tip width along with a highaspect ratio and vertical profile is provided together with muchimproved critical dimension control.

In operation, the technique of the present invention allows currentstepper and process technology to be expanded beyond conventionalresolution limits due to the fact that it effectively transfers thedifficulties inherent in thick photoresist definition to anotherrelatively thin photoresist pattern definition, utilizing a RIE processto define the resultant critical dimensions. Overall, the technique ofthe present invention provides a number of advantages including theprovision of high aspect ratio and vertical properties in a sub-micronpole tip, increased optical resolution utilizing conventional stepperequipment and improved critical dimension control. Stated another way,the technique of the present invention, in utilizing a relatively thinpatterned photoresist layer for the critical pattern definition followedby a reactive ion etching operation to accurately transfer the patternfrom an upper surface through an intermediate and underlying thickphotoresist layer, allows one to effectively pattern the thickphotoresist layer by only exposing the upper thin photoresist layer. Theuse of the patterned thin photoresist layer in conjunction with theintermediate layer and underlying thick photoresist layer ultimatelyprovides much improved trackwidth control while concomitantly extendingthe useful lifetime of current stepper technology. The technique of thepresent invention also provides greater head design flexibility sinceless stringent process requirements are needed to achieve a givendesired stack height.

Particularly disclosed herein is a process for forming a pole tip in adata transducer write head, and an upper pole of a read/write head madethereby, which comprises: providing a substrate; applying a firstphotoresist layer overlying the substrate; applying an intermediatelayer overlying the first photoresist layer; applying a secondphotoresist layer overlying the intermediate layer, the secondphotoresist layer being relatively thinner than the first photoresistlayer; patterning the second photoresist layer to produce an openingtherein; etching the intermediate layer utilizing the opening as a mask;further etching the first photoresist layer through the openingutilizing the intermediate layer as another mask; forming the pole tipwithin the opening etched in the first photoresist layer; and removingthe first and second photoresist layers and the intermediate layer toexpose the pole tip.

Further disclosed herein is a read/write head for a computer massstorage device wherein an upper pole thereof is made by the process of:providing a multilayer structure comprising a first relatively thickphotoresist layer overlying a gap layer of the read/write head, anintermediate layer overlying the first relatively thick photoresistlayer and a second relatively thin photoresist layer overlying theintermediate layer; patterning the second relatively thin photoresistlayer to provide an opening therein to the intermediate layer; etchingthe intermediate layer and the first relatively thick photoresist layerwithin the opening to the gap layer; forming the upper pole within theopening etched in the first relatively thick photoresist layer; andremoving the first relatively thick and second relatively thinphotoresist layers and the intermediate layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The aforementioned and other features and objects of the presentinvention and the manner of attaining them will become more apparent andthe invention itself will be best understood by reference to thefollowing description of a preferred embodiment taken in conjunctionwith the accompanying drawings, wherein:

FIG. 1A is a simplified side elevational cut-away view of a portion ofan MR or GMR process substrate upon which a seed layer, for exampleNiFe, is deposited to a thickness of substantially between 1000 Å-2000Å;

FIG. 1B is a follow-on cross-sectional view of the structure of FIG. 1Aillustrating the application of a relatively thick coating (on the orderof substantially 8.0 μm-10.0 μm) of a first photoresist layer overlyingthe NiFe seed layer;

FIG. 1C is a follow-on cross-sectional view of the structure of FIG. 1Billustrating the additional deposition of an intermediate metal orceramic layer of on the order of substantially 0.5 μm-2.0 μm thicknessoverlying the first photoresist layer;

FIG. 1D is a follow-on cross-sectional view of the structure of FIG. 1Cillustrating the additional application of a second photoresist layer ofon the order of substantially 0.25 μm-1.0 μm in thickness overlying theintermediate metal or ceramic layer;

FIG. 1E is a follow-on cross-sectional view of the structure of FIG. 1Dillustrating the initial patterning of the second photoresist layer toproduce an opening therein;

FIG. 1F is a follow-on cross-sectional view of the structure of FIG. 1Dillustrating a first reactive etching step through the opening formed inthe patterned second photoresist layer and the underlying intermediatemetal or ceramic layer;

FIG. 1G is a follow-on cross-sectional view of the structure of FIG. 1Fillustrating a second reactive ion etching step through the openingformed in the intermediate metal or ceramic layer and the underlyingfirst photoresist layer;

FIG. 1H is a follow-on cross-sectional view of the structure of FIG. 1Gillustrating the step of electroplating NiFe material for the top polein the opening formed in the second photoresist layer, the underlyingintermediate metal or ceramic layer and the underlying first photoresistlayer;

FIG. 1I is a final follow-on cross-sectional view of the structure ofFIG. 1H showing the resultant top pole formed following the strippingaway of the first and second photoresist layers and the intermediatemetal or ceramic layer; and

FIG. 2 is a simplified, cut-away, top plan view of a conventional diskdrive constituting one possible computer mass storage device applicationof a read head produced in accordance with the technique of the presentinvention.

DESCRIPTION OF A PREFERRED EMBODIMENT

With reference now to FIG. 1A, a simplified side elevational, cut-awayview of a portion of an MR or GMR write head substrate 10 is shown. Thesubstrate 10, shown not to scale, may comprise, for example, an alumina(Al₂O₃) or other suitable write head gap layer material of on the orderof 4000 Å in thickness overlying a bottom pole of the write head (notshown) and/or a shared shield of an underlying MR or GMR read head ofvarying types as described in the aforementioned United States Patents.A seed layer 12, for example a nickel iron (NiFe) or similar magneticpole material, is deposited to a thickness of substantially between 1000Å-2000 Å. In alternative embodiments, the seed layer 12 may comprise,for example, a relatively higher magnetic moment material such as ironnitride (FeN) or cobalt nickel iron (CoNiFe).

With reference additionally now to FIG. 1B, a follow-on cross-sectionalview of the structure of FIG. 1A is shown illustrating the applicationof a relatively thick coating of a first photoresist layer 14 overlyingthe seed layer 12 (no longer illustrated for purposes of clarity) whichserves as a bottom layer in the technique of the present invention. Thefirst photoresist layer 14 may be applied to a thickness of on the orderof substantially 6.0 μm-10.0 μm. Following the coating of the firstphotoresist layer 14, it is soft baked at a suitable temperature of onthe order of 140°-160° Celsius (“C”). The photoresist utilized for thefirst photoresist layer 14 will preferably have a relatively high etchrate to reactive ion etching (“RIE”) and not decompose during thesubsequent intermediate or middle layer deposition as will be more fullydescribed hereinafter.

With reference additionally now to FIG. 1C, a follow-on cross-sectionalview of the structure of FIG. 1 is shown illustrating the additionaldeposition of an intermediate metal (or ceramic) layer 16 overlying thefirst photoresist layer 14. In a preferred embodiment, the intermediatelayer 16 is deposited to a thickness of on the order of substantially0.1 μm-2.0 μm. The material chosen for the intermediate layer 16, forexample Al₂O₃ and other metal layers, including those comprisingtitanium, (Ti) chromium (Cr) and the like, should preferably have asuitable etch rate during a first RIE etching operation as well as goodselectivity to photoresist during a subsequent second RIE etchingoperation as will be more fully described hereinafter.

With reference additionally now to FIG. 1D, a follow-on cross-sectionalview of the structure of FIG. 1C is shown illustrating the additionalapplication of a second photoresist layer 18 overlying the intermediatelayer 16. The second photoresist layer 18 is applied to a thickness ofsubstantially less than that of the first photoresist layer 14 andgenerally to a thickness of on the order of substantially 0.25 μm-1.0μm. A preferred material for the second photoresist layer 18 willexhibit good selectivity to the intermediate layer 16 during asubsequent first RIE etching operation.

With reference additionally now to FIG. 1E, a follow-on cross-sectionalview of the structure of FIG. 1D is shown illustrating the initialpatterning of the second photoresist layer 18 to produce an opening 20therein. Because the second photoresist layer 18 is relatively verythin, good line width control may be achieved during the patterningoperation.

With reference additionally now to FIG. 1F, a follow-on cross-sectionalview of the structure of FIG. 1E is shown illustrating a first reactiveion etching step through the opening 20 formed in the patterned secondphotoresist layer 18. During this first RIE operation, the underlyingintermediate layer 16 is etched utilizing the upper, or secondphotoresist layer 18 as a masking layer. The first RIE operation isconducted until the first photoresist layer 14 is reached as an endpointto the process.

With reference additionally now to FIG. 1G, a follow-on cross-sectionalview of the structure of FIG. 1F is shois shown illustrating a secondreactive ion etching step through the opening 20 formed in theintermediate layer 16. In this step, the lower, or first photoresistlayer 14 is etched utilizing the intermediate layer 16 as a maskinglayer. The selectivity of the intermediate layer 16 must be acceptablewith respect to that of the underlying first photoresist layer 14 whilethe latter must also exhibit a relatively high etch rate during thisprocess. The seed layer 12 (not shown), whether NiFe or other suitablematerial will preferably provide an acceptable etch stop, that is, itmust have a relatively low etch rate during the second RIE processingstep such that it is not appreciably etched thereby.

With reference additionally now to FIG. 1H, a follow-on cross-sectionalview of the structure of FIG. 1G is shown illustrating the step ofelectroplating NiFe (or other suitable material) for the top pole 22 ofthe write head in the opening 20 formed through the second photoresistlayer 18, the underlying intermediate layer 16 and the underlying firstphotoresist layer 14.

With reference additionally now to FIG. 1H, a follow-on cross-sectionalview of the structure FIG. 1G is shown illustrating the resultant toppole 22 formed following the stripping away of the first and secondphotoresist layers 14, 18 and the intermediate layer 16. In a preferredembodiment the height of the top pole is substantially 1.0 μm-2.5 μmwith a corresponding width of approximately 0.35 μm-1.2 μm.

With reference additionally now to FIG. 2, a simplified, cut-away, topplan view of a disk drive 30 is shown for possible use in conjunctionwith a read/write head produced in accordance with the technique of thepresent invention. The disk drive 30 comprises, in pertinent part, anumber of disks 32 which may be rotated about a central axis. Aread/write head 34, which may be produced as above-described, ispositioned by means of a positioner 30 with respect to a number ofconcentric data tracks on the surfaces 38 of the disks 32 to enable datato be written to, or read from, the magnetically hard surfaces 178thereof. The read/write head 34 hereinbefore disclosed may also beutilized in conjunction with tape drives and other computer mass storageapplications as well.

While there have been described above the principles of the presentinvention in conjunction with specific exemplary materials and processflows, it is to be clearly understood that the foregoing description ismade only by way of example and not as a limitation to the scope of theinvention. Particularly, it is recognized that the teachings of theforegoing disclosure will suggest other modifications to those personsskilled in the relevant art. Such modifications may involve otherfeatures which are already known per se and which may be used instead ofor in addition to features already described herein. Although claimshave been formulated in this application to particular combinations offeatures, it should be understood that the scope of the disclosureherein also includes any novel feature or any novel combination offeatures disclosed either explicitly or implicitly or any generalizationor modification thereof which would be apparent to persons skilled inthe relevant art, whether or not such relates to the same invention aspresently claimed in any claim and whether or not it mitigates any orall of the same technical problems as confronted by the presentinvention. The applicants hereby reserve the right to formulate newclaims to such features and/or combinations of such features during theprosecution of the present application or of any further applicationderived therefrom.

What is claimed is:
 1. A read/write head for a computer mass storagedevice including a read sensor and an associated write transducer havinga lower pole thereof with an overlying gap layer and wherein acorresponding upper pole of said write transducer is made by a processcomprising: depositing a seed layer overlying said gap layer; applying afirst photoresist layer overlying said seed layer; applying anintermediate layer overlying said first photoresist layer; applying asecond photoresist layer overlying said intermediate layer, said secondphotoresist layer being relatively thinner than said first photoresistlayer; patterning said second photoresist layer to produce an openingtherein; etching said intermediate layer utilizing said opening as amask; further etching said first photoresist layer through said openingutilizing said intermediate layer as another mask; forming said upperpole within said opening etched in said first photoresist layer; andremoving said first and second photoresist layers and said intermediatelayer to expose said upper pole.
 2. The read/write head of claim 1wherein said gap layer comprises Al₂O₃.
 3. The read/write head of claim1 wherein said seed layer comprises NiFe.
 4. The read/write head ofclaim 1 wherein said seed layer is substantially 1000 Å-2000 Å inthickness.
 5. The read/write head of claim 1 wherein said firstphotoresist layer is substantially between 8.0 μm and 10.0 μm inthickness.
 6. The read/write head claim 1 wherein said intermediatelayer comprises a metal or ceramic layer.
 7. The read/write head ofclaim 1 wherein said intermediate layer comprises Al₂O₃ having athickness of substantially 0.μm-2.0 μm.
 8. The read/write head of claim1 wherein said second photoresist layer has a thickness of substantiallybetween 0.25 μm and 1.0 μm.
 9. The read/write head of claim 1 whereinsaid upper pole is plated upon said seed layer within said opening inetched in said first photoresist layer to a height of substantiallybetween 1.0 μm-4.5 μm.
 10. The read/write head of claim 1 furthercomprising: a head disk assembly; at least one magnetic storage mediarotatably contained within said head disk assembly having data encodablethereon; and at least one positioner mechanism movably contained withinsaid head disk assembly for positioning said read/write head withrespect to said storage media to enable reading and/or writing ofselected portions of said data.
 11. A read/write head for a computermass storage device wherein an upper pole thereof is made by the processof: providing a multi-layer structure comprising a first relativelythick photoresist layer overlying a gap layer of said read/write head,an intermediate layer overlying said first relatively thick photoresistlayer and a second relatively thin photoresist layer overlying saidintermediate layer; patterning said second relatively thin photoresistlayer to provide an opening therein to said intermediate layer; etchingsaid intermediate layer and said first relatively thick photoresistlayer within said opening to said gap layer; forming said upper polewithin said opening etched in said first relatively thick photoresistlayer; and removing said first relatively thick and second relativelythin photoresist layers and said intermediate layer.
 12. The read/writehead of claim 11 wherein said gap layer comprises Al₂O₃.
 13. Theread/write head of claim 11 further comprising a seed layer overlyingsaid substrate and underlying said first relatively thick photoresistlayer.
 14. The read/write head of claim 13 wherein said seed layercomprises substantially 1000 Å-2000 Å of NiFe.
 15. The read/write headof claim 11 wherein said first relatively thick photoresist layer issubstantially between 6.0 μm and 10 μm in thickness.
 16. The read/writehead claim 11 wherein said intermediate layer comprises a metal orceramic layer.
 17. The read/write head of claim 11 wherein saidintermediate layer comprises Al₂O₃ having a thickness of substantially0.1 μm-2.0 μm.
 18. The read/write head of claim 11 wherein said secondrelatively thin photoresist layer has a thickness of substantiallybetween 0.25 μm and 1.0 μm.
 19. The read/write head of claim 13 whereinsaid upper pole is plated upon said seed layer within said openingetched in said first relatively thick photoresist layer to a height ofsubstantially between 1.0 μm-4.5 μm.
 20. The read/write head of claim 11further comprising: a head disk assembly; at least one magnetic storagemedia rotatably contained within said head disk assembly having dataencodable thereon; and at least one positioner mechanism movablycontained within said head disk assembly for positioning said read/writehead with respect to said storage media to enable reading and/or writingof selected portions of said data.